He tried with the key on then started with the same effect. Yes I added a stereo and grounded the wire to the amp.
The prev codes where O2 sensor, rough ride and something about purge valve.
The rough ride code came up cause the PO cut the wires to the sensors and I respliced connectios.

When the code came back on I found that an O2 sensor was hand loose.
i tighten that and a few bolts on the manifold.

I havent done anything else to the truck since the last reset except the stereo

You can't ground the wire at the amp. The signals flow through it. If you removed the amp you have to connect the incoming and out going ground wires together and the ECU should communciate correctly.
Its part of the wiring for the Uk style security system that NAS 90s don't have, but the wires have to be connected for the ECU to use the diagnostic port.

If you want to get real tricky if you run the engine, then shut it off and turn the key to the "accessory" position you'll have a 15 second window tro view and clear codes. Sucks to do it that way though, just fix the amp wiring and you'll be set.

We see that all the time.

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Yes and No on the scanner.
If the ECU will communicate an OBDII scanner will work, but you have to fix the ECU wiring first otherwise a cheap scanner or a costly Rovacom can't do it (unless you use that 15 second window).

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My scanner also displays pending codes. So, if it's a code set after several fault cycles you will be alerted. If it's an instant code then clear it just before you go in for smog and hope it doesn't reappear when the shop restarts the truck.

Of course, if the code leads you to a simple repair, you should take care of it first.

Turns out that there were two causes ... (1) the dealer tech had removed & replaced the computer - since the code was exhibited previously - and forgot a ground wire, and (2) there was a software update available that hadn't been installed yet.

As much as I hate to say it ... ssshhh, the light hasn't been on for the past couple of years ...

Thursday night I bought a OB II tool and cleared all the codes. drove the truck about 30 miles without issue.
Took off work friday to go get my sticker and paint and install my slick rock sliders. The sliders have had some good use but are rock solid.
I woke up 7:00 to go get my sticker and it was raining. I turned on my wipers and the werent working . (blown fuse). So I drove to the parts store to get a 20 amp fuse and when i started the truck the light was back on. But my wipers now work.
I decided it was better to get a rejection sticker than play around with it . so went to the inspection station. there where 2 people ahead of me so i hooked my OBII tool and the code cleared.
drove in and shut the truck down and when i started it agin the light was on.

The guy hooked it up to the machine and it couldnt communicate.
Could it be the pig tail has an issue?
I know I have other problem as 4 codes came up

443
1193
1317
3999
I know that 443 is the purge valve circuit malfuntion but dont know the others.
anybody got the definitions on the codes?
Thanks

Thanks Art
443 = Evap purge valve open
1193= O 2 sensor heater circuit open down stream
1317= abs rough ride line low fault
3999= ?? cant find this one did a google search nothing cae up of importance.
could I have a bad ground causing these codes or is it something deeper

Ron

the light comes on all the time. when it was reset it came on for a second then off.
Ill check the computer to make sure its not wet.
the cover is off right now.

The truck runs and drive great no drivabilty issue. Just drove 250 miles over the weekend and did some light off roading on Nauset Beach.